474 



an misjinmetrioal distribution of tlie inagiietii* foiee does not canse 

 any error in the determinations. 



Some (iifüculty arose in finding the right form and the right 

 material, that allows the cnrient to l)e taken off' from the collector 



Fig 6 ''^^'■ 



nninterrnpledly during a long time. In one respect the conditions 

 are not very exigent: tluxions in the strength of the current by 

 changes of the resistance at the collector up to one percent can be 

 allowed in practice withont anj' reserve. On the other hand the 

 reliability of the working must be guaranteed at a minimum of 

 care and looking after. By making the diameter of the collector not 

 to exceed some millimeters and by taking silver both for the 

 collector and for the collectoi' springs a method of transmission of 

 the current was arrived at which gave excellent results during a 

 long time at a stretch, without any greasing or oiling. 



A freely suspended magnet cannot be prevented from executing 

 slight oscillations in consequence of incidental accelerations and 



